In laparoscopic surgery, access to the surgical site is gained by small a incision in the body wall through which cannulas are passed. The cannula is essentially a tube equipped with a valve to prevent loss of gas which has been used to inflate the body cavity. Various instruments are inserted into the body cavity through the cannula. One or more cannulas can be used during a procedure, and sometimes as many as four or six can be used during a given procedure. During the procedure, the surgeon manipulates the instruments in the cannulas, sometimes using more than one instrument at a time.
The action of the surgeon in manipulating the instruments causes frictional forces between the instrument and the cannula valve, which results in cannula movement responsive to movements of the instruments by the surgeon's hand. The potential exists for the cannula slipping out of the body wall, which causes a loss of pneumoperitoneum. This situation creates difficulty of reinserting the cannula and delays the procedure.
In the past, cannulas have been attached to the body wall by separate mechanisms. One mechanism engages the underside of the body wall to prevent cannula pullout. The other mechanism is put in place outside the body wall to prevent the cannula from being pushed in. These separately actuable mechanisms for securing the cannula against pull out or push in present problems in reliability of engagement to the body wall and difficulty in obtaining the necessary fixation of the cannula to the body wall. Several prior designs have involved toggle bolt-type operation, which has resulted in needless tissue trauma in the area inside the body wall, and a cumbersome procedure to engage the cannula.
In the past, various mechanisms have been used to secure placement of a variety medical devices. Some have employed a sliding sleeve technique which, upon longitudinal movement, causes a flexible member to bend outwardly adjacent the distal end of the instrument. Toward the proximal end, a flange or other mechanical means are employed so that the flexible member and the flange help to retain the instrument. Typical of such devices are U.S. Pat. No. 3,713,447; German Patent No. 2238508 (German equivalent of U.S. Pat. No. 3,713,447); German Patent No. 4021153A1 (mechanical linkage at distal end); European Patent No. 0432363A2; European Patent No. 0368473 and its U.S. equivalent, U.S. Pat. No. 4,995,868. Yet, other fixating mechanisms for insertable instruments into the body have featured a toggle-type mechanism at the distal end of the instrument to fixate it within the body wall. Typical of such devices are the Gazayerli Endoscopic Retractor Model 1 which has a toggle assembly at the distal end. Also along this line is German Patent No. 640126, which has alternative embodiments of a toggle arrangement that recedes into a sleeve, as well as a flexible member that can be expanded from the proximal end of the instrument. French Patent No. 748666 has pivoting members that flip up upon the shifting of a sleeve to retain the trocar to the inside of the body opening. Other toggle-type arrangements at the distal end are shown in British Patent No. 11277; U.S. Pat. Nos. 4,608,695; 3,261,357; and 3,039,468. Other devices employ longitudinal cutouts in a sleeve member, making its distal end flexible when subjected to a compressive force. The radial expansion assists in positioning of the instrument. Typical of such devices are U.S. Pat. Nos. 5,053,009; 1,621,159; 4,250,873; and 4,699,611. German Patent Nos. 647326 and 641240 again illustrate flexible sleeves expanding radially outwardly at the distal end of the instrument under a compressive force to assist in holding the position of the instrument. U.S. Pat. No. 3,717,151 has a plurality of fingers which are biased radially outwardly to prevent pullout of a flesh-penetrating apparatus. U.S. Pat. No. 4,861,334 uses a balloon to hold the position of a gastronomy tube. Other patents illustrating the use of inflatable means to either assist in retaining the position of an instrument or for other purposes are U.S. Pat. Nos. 4,244,033 and 4,198,981.
What has been lacking in prior designs is a simple-to-use and simple-to-build reliable mechanism for fixating the cannula with respect to the body wall. Another feature which is desirable and not present in the prior designs is a simple-to-control fixating mechanism which requires minimal manipulation to deploy, decreasing the possibility of damaging body tissue. Further, it is desirable to have a device which is sensitive to the surrounding tissue and the body wall, yet, at the same time, acts closely inside and outside the body wall to firmly and securely hold the cannula in the desired position as the procedure progresses. Also, it is desirable to have a device which is adjustable to a range of body wall thicknesses. Those, and other, advantages of the invention will be described below.